Electron gun structure



Jan. 21, 1964 E. ATTI ETAL ELECTRON GUN STRUCTURE Filed June 23. 1960Fig. 3b

Fig. 30 25 29 INVENTORS Eros AMI 8 Billy G. Douglass m ATTORNEYWITNZ/IITISSES {/Q 52/ 146%,

3,119,035 ELECTRON GUN STRUCTURE Eros Atti and Biliy G. Douglass,Horseheads, N.Y., as-

slgnors to Westinghouse Electric Corporation, East Pittsburgh, Pa., acorporation of Pennsylvania Filed June 23, 1960, Ser. No. 38,355 6Claims. (Cl. 31382) This invention relates generally to electron gunsand, more particularly, to an electron gun structure which mayincorporate a multi-electrode amplifier. The invention is applicable tocathode ray tubes of various types and provides precise beam formingelectrode alignment under both normal and severe environmentalconditions.

In accordance with U.S. Patent 3,065,368, filed December 27, 1957,entitled Electron Device, by E. Atti and assigned to the same assigneeas the present invention, an electron gun is provided having a hightransconductance. Within the gun structure, there is included a triodeamplifier. A video signal is applied to the grid of the amplifier. Thetriode plate and the first accelerating anode or screen grid of theelectron gun are electrically connected. Since these two electrodesoperate at the same potential, a large change in beam current can beeffected by a small change in applied signal. This provides means ofmaking guns of greatly increased transconductance. Additional structuresfor high transconductance guns are provided in U.S. Patents 3,065,375and 3,065,376, filed July 14, 1958, by E. Atti and assigned to the sameassignee as the present invention.

In the structure disclosed in U.S. Patent 3,065,368, mechanical supportof the various gun electrodes is provided by beading them to strong,rigid insulating rods, usually of glass. The gun screen grid and triodeplate are constituted of a metallic member which substantially encirclesthe cathode and the grid of the triode amplifier and forms a box-likesupport member for a pair of insulating spacers at the sides of the gun.The control grids of both the gun and the amplifier and the cathode aresupported in turn by extensions through the insulating spacers. Of thisunitary structure comprising the screen grid, control grids, cathode andplate only the gun screen grid and plate are directly and rigidly joinedto the remaining gun electrodes. The gun control grid, whose apertureshould be accurately aligned with the screen grid aperture, is notdirectly joined. Therefore, the gun control grid is not provided thesame rigidity of structure and exact aperture positioning as is affordedthe gun screen grid.

Under even moderately severe environmental conditions of shock andvibration it is quite possible that the insulating spacers, generally ofmica or the like on account of the excellent machinability properties ofthis type of material, can flex or slightly change their location uponthe box-like support member to which they are fastened. As a result thethree electrodes which are indirectly supported, namely the gun controlgrid, the cathode and the triode amplifier grid, may change theirposition in relation to the gun screen grid and consequently to theremaining part of the gun rigidly associated with said screen grid asexplained above.

As far as the cathode and triode amplifier grid are concerned, thisdisplacement would not be objectionable in general since theseelectrodes are not subject to critical alignment requirements. This isnot true however of the gun control grid. A lateral displacement of aninsulating spacer perpendicular to the guns axis of only a fewthousandths of an inch would cause the control grid aperture to movewith respect to the screen grid aperture by substantially the sameamount thereby introducing misalignment between these two aperturescausing unfavorable efiects upon the electron optics of the Sttes atentgun. In the case of very fine spot guns, misalignment of these twoapertures by as little as one thousandth of an inch can cause seriousdegradation in the resolution capability of the gun.

In order to provide a gun structure capable of maintaining the alignmentcarefully built into the gun during manufacture, it is desirable torigidly secure both the screen grid and the gun control grid to theremaining gun electrodes.

Any modification in the previously disclosed structure should preferablymake use of basic components applicable to both a new hightransconductance gun and to a conventional low transconductance gunwhich does not include the triode amplifier. While it is a problem todesign a gun structure wherein the screen grid and control grid areaccurately aligned when the structure is to be used in only one type ofgun, either with a triode amplifier or without a triode amplifier, theproblem is magnified when versatility as well as ruggedness is desired.

It is, therefore, an object of the present invention to provide anelectron gun wherein precise alignment between the apertures of the guncontrol grid and the screen grid may be maintained under severeenvironmental conditions as well as in ordinary use.

Another object is to provide an improved electron gun-amplifiercombination wherein planar electrodes of the triode amplifier andcylindrical electrodes of the gun electron optical system are combinedin a monolithic structure.

Another object is to provide a basic type of electron gun structurewhich may be employed equally Well in either high or lowtransconductance forms.

According to the present invention, an electron gun structure isprovided which includes a flat cathode having on one side thereof a guncontrol grid and screen grid. 'On the opposite side of the cathode is amember which may be called a plate support. The plate support and thegun control grid are beaded to insulating members which also support thescreen grid and possibly other gun electrodes. In addition, the platesupport and the gun control grid have peripheral ears or the like onwhich insulating spacer members will be mounted utilizing suitable holesin said members. These insulating members in turn support and space thecathode and additional electrodes which may comprise a triode amplifierutilizing the same cathode as the electron gun from which electronemission occurs from both sides.

The features of the present invention which are believed to -be novelare set forth with particularity in the appended claims. The presentinvention, both as to its organization and manner of operation, togetherwith the above-mentioned and further objects and advantages thereof, maybest be understood by reference to the following description, taken inconnection with the accompanying drawings, in which:

FIGURE 1 is a perspective view of part of an electron gun constructed inaccordance with the present invention;

FIG. 2 is an elevation view of the electron gun structure of FIG. 1, and

FIGS. 3a and 3b are perspective views of portions of electron gunstructures in accordance with the present invention.

Referring now to FIGS. 1 and 2, there is shown, in ascending order fromthe stem 10, a pair of rigid supports 12, a plate support 14, a triodecontrol grid 16, a cathode 18, a gun control grid 20, a firstaccelerating grid or screen grid 22 and other gun electrodes 31. A pairof insulating spacers 23 and 24 are disposed on opposite sides of thegun and have apertures therein through which portions of the platesupport 14, the triode control grid 16, the cathode 18 and the guncontrol grid are disposed. In addition, ear portions and 2a of the platesupport -14 and the control grid 20, respectively, are beaded to twopairs of insulating rods 27 and 28 disposed on opposite sides of the gunstructure. Also beaded to the insulating rods are the screen grid 22together with some or all of the remaining electrodes of the gun 31.

Leads from the various gun electrodes would ordinarily be connected tothe pins extending through the top of the stem 10. These leads are notshown so that the figures show the gun structures more clearly. Theremaining electrodes 31 are generally employed remote from the stem 10of the tube for focusing and acceleration. These electrodes may beconventional and will not be discussed herein. They will ordinarily bejoined by beading to the structure shown.

The base support members 12 are shown as a pair of rigid metallicmembers in a U-shaped configuration. The ends of the members are weldedto the stern leads while the bottom of the U portion is joined bywelding to the plate support member 14.

The plate support member 14 may simply be a continuous flat plate havinga pair of ears on each side. Two opposite pairs 25 are S8Jid ininsulating members 27 and 28 extending along the gun. The remaining twoopposite pairs extend through and help support insulating spacer members23 and 24.

When a triode amplifier is incorporated Within the gun structure, theplate support 14 can be formed so as to provide the plate 29 as anintegral part as shown in FIG. 3a. A separate support 14 and plate 29can also be used as shown in FIG. 31; making it possible to select aplate of a particular height for a particular purpose.

The control grid 16 may be a planar grid such as a frame grid or othersuitable type grid. The cathode 18 may be a conventional fiat type asfound in ordinary receiving tubes capable of emitting electrons fromopposite sides for the high transconductance gun and from one side onlyin the case of a conventional low transconductance gun.

The control grid 20 is generally of the same configuration as the platesupport 14. However, an aperture is provided therein for transmission ofthe electron beam from the cathode 18. This aperture is held in precisealignment with the aperture of the accelerating grid 22 because bothmembers are joined to the insulating members 27 and 28 along the gun. Anadditional feature of the control grid 20 is that it may be formed so asto provide shielding of the cathode from external fields and thusprevent leakage of cathode current to other gun electrodes.

It should be noted that the structure in accordance with the presentinvention is not limited to one wherein a triode amplifier isincorporated in the gun. Because of some advantages of flat cathodesover the cylindrical type, it is often desirable to employ the generalstructure shown including the plate support 14 but without the anode 29and control grid 16 comprising the amplifier.

It is seen that the present structure provides precise aperturealignment between the control grid 20 and the acceleration grid 22. Italso permits the use of a flat cathode 18 which serves as the cathode ofboth the electron gun per se and the amplifier triode incorporatedtherein, providing a very high transconductance device in accordancewith the teachings of the beforementioned copending applications.

It should be noted that the electrodes and components of a gun structurein accordance with the present invention are of simple design and may beformed by well known, inexpensive methods making ease of fabrication,whether in high or low transconductance gun types, an inherent featureof this design. The structure portion comprising the plate support 14and the gun control grid 20 may be aligned with the accelerating grid 22and sub- 4 sequent electrodes 31 of the gun and beaded together in asingle operation. Furthermore, the screen grid 22 and subsequentfocusing and accelerating electrodes 31 may be entirely conventional.

Additional versatility is built into gun structures in accordance withthe present invention because of the fact that the insulating spacers 23and 24 may be standardized so that one aperture pattern can be used fora variety of guns. That is, the spacing between the plate support andgun control grid may be maintained fixed, but the height of the anodeused and therefore its spacing from the triode grid may be varied toobtain different triode amplification factors.

The gun structure is freed from mechanical stress because the rigidsupports 12 make it possible to use lightweight and flexible connectionsto the gun components which need not provide support as well.

While the present invention has been shown in one form only, it will beobvious to those skilled in the art that it is not so limited but issusceptible of various changes and modifications without departing fromthe spirit and scope thereof.

We claim as our invention:

1. An electron gun structure comprising a cathode, a control grid and ascreen grid located on one side of said cathode for forming an electronbeam; a plate support member located on the opposite side of saidcathode from said control grid and said screen grid, said plate supportand said control grid supporting at their extremities insulating spacerplate-like members through which said cathode extends, said platesupport, said control grid and said screen grid being mutually securedto rigid insulatin g elongated rod-like members.

2. An electron gun structure for forming an electron beam comprising aflat cathode, a first beam forming electrode spaced from said cathode, asecond beam forming electrode spaced from said first beam formingelectrode remote from said cathode, a support member spaced from saidcathode on the side thereof remote from said first and second beamforming electrodes and transverse to said electron beam, 2. pair ofinsulating spacer plate members having apertures therein through whichportions of said cathode, said first beam forming electrode and saidsupport member extend, and one or more rigid insulating rod-like membersmechanically secured to said first and second beam forming electrodesand to said support member.

3. An electron gun structure comprising a flat cathode having anelectron emissive surface, a first beam forming electrode spaced fromsaid cathode, a second beam forming electrode spaced from said firstbeam forming electrode remote from said cathode, said first and secondbeam forming electrodes having, respectively, first and second beamapertures aligned and positioned directly over said electron emissivesurface of said cathode, a support member spaced from said cathode onthe side thereof remote from said first and second beam formingelectrodes, a pair of insulating spacer plate-like members havingapertures therein through which portions of said cathode, said firstbeam forming electrodes and said support member extend, and one or morerigid insulating rod-like members mechanically secured to said first andsecond beam forming electrodes and to said support memher.

4. An electron gun structure, disposed within an envelope including astem member, comprising a flat cathode having an electron emissivesurface, a first beam forming electrode spaced from said cathode, asecond beam forming electrode spaced from said first beam formingelectrode remote from said cathode, said first and second beam formingelectrodes having, respectively, first and second beam apertures alignedand positioned directly over electron emissive surfaces of said cathode,a support member spaced from said cathode on the side thereof remotefrom said first and second beam forming electrodes, a pair of insulatingspacer plate-like members having apertures therein through whichportions of said cathode, said first beam forming electrode and saidsupport member extend, two or more rigid insulating rod-like membersmechanically secured to said first and second beam forming electrodesand to said support member, and one or more rigid mounting membersmechanically secured to said support member and to said stern member.

5. An electron gun structure, disposed within an envelope including astem member, comprising a flat cathode having two oppositely disposedelectron emissive surfaces, a first beam forming electrode spaced fromsaid cathode, a second beam forming electrode spaced from said firstbeam forming electrode remote from said cathode, a suppont member spacedfrom said cathode on the side thereof remote from said first and secondbeam forming electrodes, a grid spaced from and disposed between saidcathode and said support member, an anode disposed on said supportmember, a pair of insulating spacer plate-like members having aperturestherein through which portions of said cathode, said first beam formingelectrode, said support member, and said grid extend, two or more rigidinsulating rod-like members mechanically secured to said first andsecond beam forming electrodes and to said support member, and rigidmounting means secured to said support member and to said stem member.

6. An electron gun structure disposed within an envelope including astem member as a portion thereof, comprising a flat cathode having twooppositely disposed electron emissive surfaces, an electron gun controlgrid spaced 30 from said cathode, an electron gun screen grid and othergun electrodes spaced from said electron gun control grid remote fromsaid cathode, said electron gun control grid and said electron gunscreen grid having beam apertures therein mutually aligned with said oneof said electron emissive surfaces of said cathode, a plate supportmember spaced from said cathode on the side thereof remote from saidelectron gun control grid and said electron gun screen grid, anamplifier control grid disposed between and spaced from said cathode andsaid plate support member, an anode supported directly by said platesuppont member, said electron gun control grid and said plate supportmember each having four side edges defining planes substantiallyperpendicular to the axis of the electron gun, each of said side edgeshaving a pair of ear members jutting out therefrom, a pair of spacermembers of insulating material having apertures therein, each of saidspacer members having extending therethrough the two ears on one side ofsaid electron gun control grid, the two ears on one side of said platesupport member and portions of said cathode and said amplifier controlgrid, two or more rigid members of a glass-like insulating materialmechanically securing by beading to the four remaining ear portions oneach of said plate support members and said electron gun control gridand to said electron gun screen grid and to said other gun electrodes,and one or more rigid mounting members mechanically secured to saidsupport member and to said stem member.

Schade Oct. 22, 1940 Bareiss Mar. 5, 1946

1. AN ELECTRON GUN STRUCTURE COMPRISING A CATHODE, A CONTROL GRID AND ASCREEN GRID LOCATED ON ONE SIDE OF SAID CATHODE FOR FORMING AN ELECTRONBEAM; A PLATE SUPPORT MEMBER LOCATED ON THE OPPOSITE SIDE OF SAIDCATHODE FROM SAID CONTROL GRID AND SAID SCREEN GRID, SAID PLATE SUPPORTAND SAID CONTROL GRID SUPPORTING AT THEIR EXTREMITIES INSULATING SPACERPLATE-LIKE MEMBERS THROUGH WHICH SAID CATHODE EXTENDS, SAID PLATESUPPORT, SAID CONTROL GRID AND SAID SCREEN GRID BEING MUTUALLY SECUREDTO RIGID INSULATING ELONGATED ROD-LIKE MEMBERS.